UV - Visible and1H or13C NMR spectroscopic studies on the specific interaction between lithium ions and the anion from tropolone or 4-isopropyltropolone (hinokitiol) and on the formation of protonated tropolones in acetonitrile or other solvents

Masashi Hojo, Tadaharu Ueda, Tomonori Inoue, Michitaka Ike, Masato Kobayashi, Hiromi Nakai

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    Abstract

    The specific interaction between lithium ions and the tropolonate ion (C7H5O2 -: L-) was examined by means of UV - visible and 1H or 13C NMR spectroscopy in acetonitrile and other solvents. On the basis of the electronic spectra, we can propose the formation of not only coordination-type species (Li+(L-)2) and the ion pair (Li +L-) but also a "triple cation" ((Li +)2L-) in acetonitrile and acetone; however, no "triple cation" was found in N,N-dimethylformamide (DMF) and in dimethylsulfoxide (DMSO), solvents of higher donicities and only ion pair formation between Li+ and L- in methanol of much higher donicity and acceptivity. The 1H NMR chemical shifts of the tropolonate ion with increasing Li+ concentration verified the formation of (Li+)2L- species in CD 3CN and acetone-d6, but not in DMF-d6 or CD3OD. With increasing concentration of LiClO4 in CD 3CN, the 1H NMR signals of 4-isopropyltropolone (HL′) in coexistence with an equivalent amount of Et3N shifted first toward higher and then toward lower magnetic-fields, which were explained by the formation of (Li+)(Et3NH+)L′ - and by successive replacement of Et3NH+ with a second Li+ to give (Li+)2L′ -. In CD3-CN, the 1,2-C signal in the 13C NMR spectrum of tetrabutylammnium tropolonate (n-Bu4NC7H 5O) appeared at an unexpectedly lower magnetic-field (184.4 ppm vs TMS) than that of tropolone (172.7 ppm), while other signals of the tropolonate showed normal shifts toward higher magnetic-fields upon deprotonation from tropolone. Nevertheless, with addition of LiClO4 at higher concentrations, the higher and lower shifts of magnetic-fields for 1,2-C and other signals, respectively, supported the formation of the (Li +)2L- species, which can cause redissolution of LiL precipitates. All of the data with UV - visible and 1H and 13C NMR spectroscopy demonstrated that the protonated tropolone (or the dihydroxytropylium ion), H2L+, was produced by addition of trifluoromethanesulfonic or methanesulfonic acid to tropolone in acetonitrile. The order of the 5-C and 3,7-C signals in 13C NMR spectra of the tropolonate ions was altered by addition of less than an equivalent amount of H+ to the tropolonate ion in CD3CN. Theoretical calculations satisfied the experimental 13C NMR chemical shift values of L-, HL, and H2L+ in acetonitrile and were in accordance with the proposed reaction schemes.

    Original languageEnglish
    Pages (from-to)1759-1768
    Number of pages10
    JournalJournal of Physical Chemistry B
    Volume111
    Issue number7
    DOIs
    Publication statusPublished - 2007 Feb 22

    Fingerprint

    Tropolone
    Acetonitrile
    Lithium
    acetonitrile
    Anions
    Negative ions
    lithium
    Nuclear magnetic resonance
    Ions
    anions
    nuclear magnetic resonance
    ions
    interactions
    Magnetic fields
    Dimethylformamide
    Chemical shift
    Acetone
    magnetic fields
    acetone
    Nuclear magnetic resonance spectroscopy

    ASJC Scopus subject areas

    • Physical and Theoretical Chemistry

    Cite this

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    title = "UV - Visible and1H or13C NMR spectroscopic studies on the specific interaction between lithium ions and the anion from tropolone or 4-isopropyltropolone (hinokitiol) and on the formation of protonated tropolones in acetonitrile or other solvents",
    abstract = "The specific interaction between lithium ions and the tropolonate ion (C7H5O2 -: L-) was examined by means of UV - visible and 1H or 13C NMR spectroscopy in acetonitrile and other solvents. On the basis of the electronic spectra, we can propose the formation of not only coordination-type species (Li+(L-)2) and the ion pair (Li +L-) but also a {"}triple cation{"} ((Li +)2L-) in acetonitrile and acetone; however, no {"}triple cation{"} was found in N,N-dimethylformamide (DMF) and in dimethylsulfoxide (DMSO), solvents of higher donicities and only ion pair formation between Li+ and L- in methanol of much higher donicity and acceptivity. The 1H NMR chemical shifts of the tropolonate ion with increasing Li+ concentration verified the formation of (Li+)2L- species in CD 3CN and acetone-d6, but not in DMF-d6 or CD3OD. With increasing concentration of LiClO4 in CD 3CN, the 1H NMR signals of 4-isopropyltropolone (HL′) in coexistence with an equivalent amount of Et3N shifted first toward higher and then toward lower magnetic-fields, which were explained by the formation of (Li+)(Et3NH+)L′ - and by successive replacement of Et3NH+ with a second Li+ to give (Li+)2L′ -. In CD3-CN, the 1,2-C signal in the 13C NMR spectrum of tetrabutylammnium tropolonate (n-Bu4NC7H 5O) appeared at an unexpectedly lower magnetic-field (184.4 ppm vs TMS) than that of tropolone (172.7 ppm), while other signals of the tropolonate showed normal shifts toward higher magnetic-fields upon deprotonation from tropolone. Nevertheless, with addition of LiClO4 at higher concentrations, the higher and lower shifts of magnetic-fields for 1,2-C and other signals, respectively, supported the formation of the (Li +)2L- species, which can cause redissolution of LiL precipitates. All of the data with UV - visible and 1H and 13C NMR spectroscopy demonstrated that the protonated tropolone (or the dihydroxytropylium ion), H2L+, was produced by addition of trifluoromethanesulfonic or methanesulfonic acid to tropolone in acetonitrile. The order of the 5-C and 3,7-C signals in 13C NMR spectra of the tropolonate ions was altered by addition of less than an equivalent amount of H+ to the tropolonate ion in CD3CN. Theoretical calculations satisfied the experimental 13C NMR chemical shift values of L-, HL, and H2L+ in acetonitrile and were in accordance with the proposed reaction schemes.",
    author = "Masashi Hojo and Tadaharu Ueda and Tomonori Inoue and Michitaka Ike and Masato Kobayashi and Hiromi Nakai",
    year = "2007",
    month = "2",
    day = "22",
    doi = "10.1021/jp066756n",
    language = "English",
    volume = "111",
    pages = "1759--1768",
    journal = "Journal of Physical Chemistry B Materials",
    issn = "1520-6106",
    publisher = "American Chemical Society",
    number = "7",

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    TY - JOUR

    T1 - UV - Visible and1H or13C NMR spectroscopic studies on the specific interaction between lithium ions and the anion from tropolone or 4-isopropyltropolone (hinokitiol) and on the formation of protonated tropolones in acetonitrile or other solvents

    AU - Hojo, Masashi

    AU - Ueda, Tadaharu

    AU - Inoue, Tomonori

    AU - Ike, Michitaka

    AU - Kobayashi, Masato

    AU - Nakai, Hiromi

    PY - 2007/2/22

    Y1 - 2007/2/22

    N2 - The specific interaction between lithium ions and the tropolonate ion (C7H5O2 -: L-) was examined by means of UV - visible and 1H or 13C NMR spectroscopy in acetonitrile and other solvents. On the basis of the electronic spectra, we can propose the formation of not only coordination-type species (Li+(L-)2) and the ion pair (Li +L-) but also a "triple cation" ((Li +)2L-) in acetonitrile and acetone; however, no "triple cation" was found in N,N-dimethylformamide (DMF) and in dimethylsulfoxide (DMSO), solvents of higher donicities and only ion pair formation between Li+ and L- in methanol of much higher donicity and acceptivity. The 1H NMR chemical shifts of the tropolonate ion with increasing Li+ concentration verified the formation of (Li+)2L- species in CD 3CN and acetone-d6, but not in DMF-d6 or CD3OD. With increasing concentration of LiClO4 in CD 3CN, the 1H NMR signals of 4-isopropyltropolone (HL′) in coexistence with an equivalent amount of Et3N shifted first toward higher and then toward lower magnetic-fields, which were explained by the formation of (Li+)(Et3NH+)L′ - and by successive replacement of Et3NH+ with a second Li+ to give (Li+)2L′ -. In CD3-CN, the 1,2-C signal in the 13C NMR spectrum of tetrabutylammnium tropolonate (n-Bu4NC7H 5O) appeared at an unexpectedly lower magnetic-field (184.4 ppm vs TMS) than that of tropolone (172.7 ppm), while other signals of the tropolonate showed normal shifts toward higher magnetic-fields upon deprotonation from tropolone. Nevertheless, with addition of LiClO4 at higher concentrations, the higher and lower shifts of magnetic-fields for 1,2-C and other signals, respectively, supported the formation of the (Li +)2L- species, which can cause redissolution of LiL precipitates. All of the data with UV - visible and 1H and 13C NMR spectroscopy demonstrated that the protonated tropolone (or the dihydroxytropylium ion), H2L+, was produced by addition of trifluoromethanesulfonic or methanesulfonic acid to tropolone in acetonitrile. The order of the 5-C and 3,7-C signals in 13C NMR spectra of the tropolonate ions was altered by addition of less than an equivalent amount of H+ to the tropolonate ion in CD3CN. Theoretical calculations satisfied the experimental 13C NMR chemical shift values of L-, HL, and H2L+ in acetonitrile and were in accordance with the proposed reaction schemes.

    AB - The specific interaction between lithium ions and the tropolonate ion (C7H5O2 -: L-) was examined by means of UV - visible and 1H or 13C NMR spectroscopy in acetonitrile and other solvents. On the basis of the electronic spectra, we can propose the formation of not only coordination-type species (Li+(L-)2) and the ion pair (Li +L-) but also a "triple cation" ((Li +)2L-) in acetonitrile and acetone; however, no "triple cation" was found in N,N-dimethylformamide (DMF) and in dimethylsulfoxide (DMSO), solvents of higher donicities and only ion pair formation between Li+ and L- in methanol of much higher donicity and acceptivity. The 1H NMR chemical shifts of the tropolonate ion with increasing Li+ concentration verified the formation of (Li+)2L- species in CD 3CN and acetone-d6, but not in DMF-d6 or CD3OD. With increasing concentration of LiClO4 in CD 3CN, the 1H NMR signals of 4-isopropyltropolone (HL′) in coexistence with an equivalent amount of Et3N shifted first toward higher and then toward lower magnetic-fields, which were explained by the formation of (Li+)(Et3NH+)L′ - and by successive replacement of Et3NH+ with a second Li+ to give (Li+)2L′ -. In CD3-CN, the 1,2-C signal in the 13C NMR spectrum of tetrabutylammnium tropolonate (n-Bu4NC7H 5O) appeared at an unexpectedly lower magnetic-field (184.4 ppm vs TMS) than that of tropolone (172.7 ppm), while other signals of the tropolonate showed normal shifts toward higher magnetic-fields upon deprotonation from tropolone. Nevertheless, with addition of LiClO4 at higher concentrations, the higher and lower shifts of magnetic-fields for 1,2-C and other signals, respectively, supported the formation of the (Li +)2L- species, which can cause redissolution of LiL precipitates. All of the data with UV - visible and 1H and 13C NMR spectroscopy demonstrated that the protonated tropolone (or the dihydroxytropylium ion), H2L+, was produced by addition of trifluoromethanesulfonic or methanesulfonic acid to tropolone in acetonitrile. The order of the 5-C and 3,7-C signals in 13C NMR spectra of the tropolonate ions was altered by addition of less than an equivalent amount of H+ to the tropolonate ion in CD3CN. Theoretical calculations satisfied the experimental 13C NMR chemical shift values of L-, HL, and H2L+ in acetonitrile and were in accordance with the proposed reaction schemes.

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